1. Field of the Invention
The present invention relates in general to energy conservation systems and more specifically to a system for controlling the coupling of power to a given area by means of a key-operated ultrasonic sound transmitter and one or more receivers associated therewith.
2. Description of the Prior Art
Prior art devices have used a radio receiver to remotely control the source of power for lighting. See, e.g., U.S. Pat. No. 2,346,889. Another prior art device enables remote control of power in a room, but its use is merely to enable different power outlets in the room to be controlled from a preexisting switch. See, e.g., U.S. Pat. No. 3,590,271 cited as being of interest in the above cited copending application. However, no prior art discloses control of power in a given room by means of a key-operated ultrasonic transmitter and one or more receivers in that room. Nor has there been found any prior art wherein the transmitter control may be overridden for example, to turn on a heater if the room temperature drops below a certain point. Such devices would have been impractical in the past due to their bulkiness and cost; factors that have ameliorated greatly with the advent of electronic integrated circuits.
The use of an ultrasonic sound signal versus a radio wave is also much more useful because a given ultrasonic sound transmitter has a localized output which will not turn on a receiver that is in another room; the sound waves are contained in the room by the walls which absorb the sound waves. No such limitation attaches to radio waves, so that for such a system, localization of a transmitter signal in a given room is much more expensive and difficult. Such localization is critically important in the operation of the present invention, for example, since one use of the system would be in hotel rooms where power in adjacent rooms would be controlled by separate independent systems according to the present invention.